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'Alien Vs. Predator': The Battle to Merge Practical Effects and CGI

Mary Ann Skweres takes on predatory aliens to find out the visual effects secrets behind Alien Vs. Predator.

Fans of the Aliens and Predators movies and comics have been waiting a long time for this film. All images  & © Twentieth Century Fox.

Fans of the Aliens and Predators movies and comics have been waiting a long time for this film. All images & © Twentieth Century Fox.

Visual effects supervisor John Bruno received an Oscar for The Abyss and a string of other nominations and awards. He worked with James Cameron for 16 years, so his unique qualifications made him the ideal candidate to take on the visual effects for Fox's sci-fi monster-meet, Alien Vs. Predator (AVP), based on the classic characters from movies of the same names.

When Fox began talking to him in June 2003 they had two questions. Can it be done? Can it be done for the money? Scheduled to shoot in Prague, only a year was allowed to complete the whole film. In the initial schedule, post was allocated a mere three months after the return from Prague to complete all the effects work an impossible schedule unless you want to throw a lot of money into the production. This was not an option. Bruno's approach was to do as much as possible in camera and supplement that work with CG.

For the aliens and a number of sets, Bruno decided to work with various scale models and miniatures, including a full-scale and below scale queen. At first Fox was skeptical. The current trend in the industry is to do most of these types of effects with computer graphics, but after budgeting for all CG, it became apparent that doing all the work in CG would be too expensive. Bruno setup his own model unit, headed by Richard Van den Bergh. Among the sets that the model unit built were a 1/6 scale 94 ft. x 36 ft. whaling station, a 30 ft. high model of an ice cliff for the film's action ending and the Alien queen's chamber inside the pyramid, including a 15 ft. long queen machine the device used for laying eggs. Because it was winter in Prague, all the sets had to be built inside. There were no spaces big enough to always build to the desired scale. Despite the creative work-arounds this approach was still a tricky proposition because in order to keep on the short schedule, all of the model shoots had to be scheduled at the same time, as first unit was shooting. At times during production four units were working at one time a first, a second, a third and a model unit. Bruno was involved in all units and worked seven days a week.

Several studios handled the f/x work, hired due to their past track records.

Several studios handled the f/x work, hired due to their past track records.

Bruno relied on the experience of his crew to make this all work. The computer animation, matte paintings, set extensions and other computer graphics were executed by several visual effects houses. Bruno chose these companies based on the work they had done previously, their availability and most importantly his ability to communicate effectively with the lead personnel. With no time to take chances, Bruno admits, "I went with people who could deliver."

Keeping true to the original design and character was important. There was a below scale Queen from the Cameron films that was used as a reference for building the full-scale model and a 4-1/2 foot puppet. A few adjustments needed to be made to address practical concerns. During one chase scene, the Queen is out in the open on the ice running against a white background. The creature's pelvis needed to be adjusted in order for her to function in a run cycle. The length of the tail was increased for aesthetic reasons and the "high heels" pointed foot extensions were removed at the request of the director. Otherwise the Aliens remained true to form.

Whoever was awarded the Aliens would also be responsible for the Alien Queen. Moving Picture Co.'s animation director, Adam Valdez, worked on The Lord of the Rings and the animation of Gollum. Bruno thought he had the background to animate the Alien Queen. Although, many of the Aliens were shot practically many parts tails, flutes on the backs and rubber parts that did not move realistically on the puppets were replaced in post with CG. Other scenes, such as the Aliens jumping off the ice ledge at the end, were done in CG because they were too dangerous to do in live action. Other scenes were too complicated to set up during production, such as the scene in the Queen's chamber where the practical Queen puppet has a swarm of baby CG Aliens crawling all over her. He also thought that MPC was a large enough company with the resources both in personnel and technology to deliver on the grueling deadline. MPC had software that enabled the animators to move the Queen around, enlarge her or change her positioning in the shot. Besides the Aliens, MPC created the Predator mother ship and the pods landing craft from the original movie.

Bringing the alien facehuggers to life took a combination of classic creature effects and CG.

Bringing the alien facehuggers to life took a combination of classic creature effects and CG.

Cinesite's 3D supervisor, Ivor Middleton, had done CG spiders for Harry Potter a similar effect to the Alien facehuggers, the small Aliens that latch onto the victim's faces. The huggers were entirely CG, dynamic and photorealistic. A resin cast of the physical Alien model aided in the modeling, as did the original film, detailed storyboards and previs. In one key sequence a Predator slices a flying hugger in half, exposing internal organs based on photographic reference of the biological structure of animals' internal organs and enhanced with 2D "ultra-slime" goo strung between the dissected halves. Middleton explains, "Our brief from director Paul Anderson was basically to `make it disgusting' and that is what we have tried to do." During production in Prague, Middleton and 2D supervisor David Rey shot live-action plates with tracking markers. A prosthetic hugger on a long pole was "flown" through the shot for lighting reference. Cinecite wrote a shader tool to virtually replicate the original set lighting onto the CG hugger. A speed ramp technique made the hugger attack more dynamic. Practical effects plates of exploding food and offal, composited over the hugger, completed the gory display. Cinesite also worked on digital matte painting, set replacement, multi-element motion control miniature composites and CG Aurora Australis.

When Bruno was originally awarding work, Framestore CFC had other feature commitments. When their schedule opened up, they jumped in to work on the ice tunnel escape scene, matte paintings and compositing. Bruno used previs extensively to define shots to his vfx teams. This method helped Framestore CFC supervisor Craig Lyn to set the camera move for the 3D-hologram shot of the whaling station. According to Craig, "The challenge was to define something that was both old and new." Another challenge for key compositor, Adrian de Wet, was the pyramid explosion and the resulting blue plasma fire. The team had to completely paint out the existing "baked" in lighting in the photographed plates and recreate the shadows, glows and other effects. The plasma fire was created using a mixture of 3D and a 2D filmed fire element. All interactive lighting was painted in as well. De Wet shares, "This was a challenging sequence editorially, and the impact of it relies heavily on critically timed choreography. There was a lot of back-and-forth until we had timings, locked under Bruno's supervision."

All the weapons in the film were CG.

All the weapons in the film were CG.

All the weapons in AVP were computer generated. Created by Double Negative, these included the Predator's wrist blade, the Predator's weapons fire and the Predator's throwing disc used to slice Aliens in half. Another effect when the Predator cloaks and uncloaks, also supplied by D-Neg, became one of Bruno's favorites. Vfx supervisor Richard Briscoe helmed the project at Double Negative.

Vit Komrzy and Universal Production Partners (UPP) in Prague had a chance to show Bruno that the Czech vfx house produces high-quality work. Their most complicated sequence were shots in the Chamber of the Gods, a completely reconfigured room with moving statues, walls and blocks of stone. In one slow-motion shot more than 30 layers were used to get the desired effect. The team also added fire flashes and sparkles to the sequence of the Alien Queen awakening in her chamber. UPP processed other shots including digital matte paintings, compositing and retouches. Because of the short schedule Komrzy comments, "We had to choose the best technology the first time. We could not take the liberty of trying and testing several methods as on other projects."

Mary Ann Skweres is a filmmaker and freelance writer. She has worked extensively in feature film and documentary post-production with credits as a picture editor and visual effects assistant. She is a member of the Motion Picture Editors Guild.